1. Field of the Invention
The present invention relates generally to connector fixtures and more particularly to such fixtures provided with an improved construction for a lug utilized to properly align a first structural member to a second structural member.
2. Description of the Prior Art
A connector fixture for joining a first structural member to a second structural member wherein one of the structural members includes lugs which are received into bores on the other structural member are well known and widely adopted in the trade. For example, such a connector fixture is disclosed in U.S. Pat. No. 3,421,280 entitled "Building Construction" and issued to Charles W. Attwood on Jan. 14, 1969 and owned by the Assignee of this application. This fixture has proved to be of particular utility in modular space frame systems as shown in the aforementioned U.S. Pat. No. 3,421,280.
The lugs on the connector fixtures serve a two fold purpose. First, the lugs serve to automatically align the first structural member to the second structural member, thereby permitting not only an easy and rapid assembly of the connector fixture but also a more accurate alignment of the structural members relative to each other than is obtainable by more conventional connector fixtures. Connector fixtures employing lugs thus not only reduce construction time, and hence construction costs, but also eliminate the necessity of tapes, protractors and the like which were previously necessary to properly align the structural members.
Secondly, connector fixtures employing lugs provide a rigid structural assembly while utilizing only a single fastener. In previously known connector fixtures without lugs, at least two bolts or the like were required in order to prevent one structural member from pivoting relative to the other structural member around the axis of the fastener. Since fasteners, such as nuts and bolts, are relatively expensive to purchase and time consuming to install, additional savings are realized by utilizing connector fixtures with lugs.
The previously known connector fixtures employing lugs have been simple in structure, typically comprising a pair of circular coined lugs in the first structural member and a pair of lug receiving recesses or apertures in the second structural member. Due to the coining operation, the abstract surface of the previously known lugs, i.e. the surface of the lug which abuts against the inner surface of the lug receiving aperture, is somewhat conical in shape. In addition, registering apertures were provided in each structural member to receive a fastener therethrough. Thus, the fastener and the lugs created a three point attachment between the structural members, thereby preventing the first structural member from pivoting relative to the second structural member around the axis of the fastener.
Connector fixtures with lugs have enjoyed wide acceptance in the trade. However, it has been found that with the previously known connector fixtures with lugs, when a torque of high magnitude is applied to the two structural members, tending to produce a pivotal motion around the fastener, the previously known coined lug has had a tendency to slip out of its receiving aperture. After the lug has escaped from its receiving aperture, the effectiveness of the connector fixture is effectively destroyed.